In a wireless telecommunications system, communication paths need to be established from an originating source to a destination source and from the destination source to the originating source. In order to establish these communication paths, the destination source should be able to intelligently read information from the originating source and the originating source should be able to intelligently read information from the destination source. The transmitters of the originating or destination sources may send information at one phase and the receivers of the destination or originating sources may receive information out of phase. In such a situation, the receivers will not know at what point in the data stream the receive process has started. Information is partitioned into frames and to adequately process the information the beginning of each frame should be identified. Conventional techniques to frame align information are cumbersome, slow in frame identification, and may lose frames of information. Therefore, it is desirable to quickly and easily identify the beginning of each frame of information to achieve proper processing.
UK patent application GB9513168.6 describes a wireless telecommunications system and method for frame aligning information. In the system described therein a central terminal transmits and receives wireless signals to and from a subscriber terminal. A downlink communication path is established from a transmitter of the central terminal to a receiver of the subscriber terminal. A downlink signal is transmitted from the transmitter to the receiver during setup and operation of the wireless telecommunications system carrying information partitioned into a plurality of frames. The downlink signal includes an overhead channel having a frame alignment signal for each frame of information. The receiver monitors the downlink signal to identify the frame alignment signal. The downlink communication path is established when the receiver identifies two successive frame alignment signals.
Although the approach described in GB9513168.6 enables the reliable establishment of a correct frame alignment, the process of frame alignment can take a not insignificant time due to the need to sequentially sample the frame alignment bits of the frame alignment word, which bits are transmitted sequentially every nth bit of the overhead channel, successive bits of the overhead channel being transmitted every mth bit of the wireless communications signal. The time taken for frame alignment can be particularly noticeable where the wireless link is lost during transmission and has to be re-established, or where frame alignment is lost due to noise or other reasons.